This invention relates in general to a mechanism for generating a pulse by switching the state of a magnetic device that has come to be known as a Wiegand wire and more particularly to a mechanism and method for affecting the magnetic field to which a Wiegand wire module is subjected so as to provide a reliable and repeatable output pulse upon the occurrence of a predetermined event.
The magnetic device employed in the pulser of this invention is of the type disclosed in U.S. Pat. No. 3,820,090 issued June 25, 1974. A preferred embodiment of this magnetic device is disclosed in co-pending application Ser. No. 897,483 filed Apr. 18, 1978, now U.S. Pat. No. 4,247,601 and entitled "Switchable Magnetic Device and Method of Manufacturing Same". These magnetic devices are ferro-magnetic wire segments which have been treated in such a fashion as to provide core and shell portions with divergent properties and in particular divergent coercivities. This type of wire has come to be known in the art as Wiegand wire.
The Wiegand wire essentially has two states. In one of these states, the magnetization of the core and shell are in opposite directions and this state may conveniently be called a reverse state. In the other state, the magnetization of the core and shell are in the same direction and this state may conveniently be called the confluent state. When the magnetic field to which the wire is subjected passes a threshold in one direction or the other, the wire switches state. The switch in state is extremely rapid so that the rate of change of flux through a pickup coil wrapped around the wire is great. As a consequence the output from the pickup coil is very substantial, in some cases being as high as 8 volts into an open circuit on a repeatable basis. The wire and pickup coil is referred to as a module.
Although certain techniques have been disclosed for switching the state of the Wiegand wire, some of these techniques have not been applied commercially in a wide range of applications because of consideration of costs or size.
Accordingly, it is a major purpose of this invention to provide a highly versatile pulser and pulsing arrangement employing a Wiegand wire module.
It is a related purpose to provide such a versatile item in a device that is simple and is relatively inexpensive to produce and to maintain.
It is another related purpose to provide the characteristics of low cost and versatility while maintaining the reliability and repeatability of result that has been provided with previously known pulse generating mechanisms employing the Wiegand wire.
Because the output pulse has to be taken off the pickup coil, it is preferable that the module, consisting of Wiegand wire segment and pickup coil, be stationary in the pulse generator and that the moving element be some ferro-magnetic element. Thus one purpose of the invention is to provide a pulser design in which the output pulse can be developed without moving the pulser unit.